Method of producing alkali metal phosphates by converting ferrophosphorus with alkali metal sulphates



Patented Aug. 4, 1951 UNITED STATES PATENT OFFICE FRITZ 'ULLMANN ANDJOSEPH BRESLAUER, OF GENEVA, AND EGI L LIE, OF GHEVRES, NEAR GENEVA,SWITZERLAND METHOD OF PRODUCING ALKALI METAL PHOSPHATES BY CONVERTINGFERROPHOS PHORUS WITH ALKALI METAL SULPHATES No Drawing. Applicationfiled July 20, 1929, Serial No. 379,876, and in Germany July 24, 1928.

" phosphates from phosphoric iron and alkali metal sulphates by heatingferro-phosphorus together with sodium sulphate and drawing out theobtained sodium phosphate by means of water. When working according tothe equation:

3 molecules of sodium sulphate are needed to 2 atoms of phosphorus and,when the process is carried out on a practical scale, it is advisable toemploy a surplus of 10 to 15 per cent of sodium sulphate.

Investigations carried out in connection with this process have shownthat the maximum yield of water soluble substances will amount to 7 2,6per cent of the amount which may be expected theoretically. Only by theuse of double the amount, i. e. six molecules, instead of 3 molecules ofalkali metal sulphates (as given in the theoretical equation), is itpossible to obtain about 90 per cent of the theoretical yield ofwater-soluble phosphates.

This excessive quantity of alkali metal sulphates which does not partakein the reaction and which contaminates the end product requires ofcourse a considerable amount of fuel, work et cetera.

It is further a matter of fact, that when commercial potassium sulphateis used, the lime and magnesia contents of the same will exert adisturbing influence, and reduce the yield of water-soluble potassiumphosphate.

We have now found, that the conversion of ferro-phosphorus by thetheoretical amount of alkali metal sulphates may be carried out when acertain percentage of a reduction agent is added and the mixture isheated to a temperature at which the reaction will take place.

Suitable reaction agents are coals or carbonaceous substances, forinstance tar or remagnesium compounds and, when this sulphate is used,the addition of the reaction agent will have an additional effect, inthat the disturbing effects of such calcium and magnesium compounds willbe avoided.

Emample.2 kg. of commercial potassium sulphate containing 47 per cent ofK O, 2,7 6 per cent of CaOandjMgOare heated with 1 kg. offerrophosphorus and with 0,06 kg. of finely pulverized coal untilsintering takes place or the mass is melted, whereupon the mass iscooled rapidly by pouring the same into water.

The yield of water-soluble potassium phosphate, which is removed fromthe melted mass in known manner, amounts to 95,1 per cent of thetheoretically calculated quantity. In the mass described above 3,04molecules of potassium sulphate are present for each two molecules ofphosphorus.

We claim:

1. A method of producing alkali metal phosphate from ferro-phosphorus,comprising heating term-phosphorus with an alkali metal sulphate in thepresence of a carbonaceous reducing agent in the proportion ofapproximately one part by weight of ferrophosphorus, approximately twoparts by weight of alkali metal sulphate, and approximately .06 part byweight of such reducing agent until reaction takes place, and separatingalkali metal phosphate from the resulting product.

2. A method of producing potassium phosphate from term-phosphorus,comprising heating term-phosphorus with potassium sulphate in thepresence of a carbonaceous reducing agent in the proportion ofapproximately one part by weight of ferro-phosphorus, approximately twoparts by weight of potassium sulphate, and approximately .06 part byweight of such reducing agent until reaction takes place, and separatingpotassium phosphate from the resulting product.

3. A method of producing sodium phosphate from term-phosphorus,comprising heating term-phosphorus with sodium sulphate in the presenceof a carbonaceous reducing agent in the proportion of approximately onepart by Weight of ferro-phosphorus approximately two parts by Weight ofsodium sulphate, and approximately .06 part by weight of such reducingagent until reaction takes place, and separating sodium phosphate fromthe resulting product.

4. A method of producing alkali metal phosphate according to claim 1wherein finely pulverized coal is employed as the reducing agent.

5. A method of producing potassium phosphate according to claim 2wherein finely pulverized coal is employed as the reducing agent.

6. A method of producing sodium phosphate according to claim 3 whereinfinely pulverized coal is employed as the reducing agent.

20 In testimony whereof We have hereunto sete chand r- FRITZ ULLMANN.JOSEPH BRESLAUER. EGIL LIE.

